This program project will investigate the hypotheses that oxidative cellular injury accompanies normal aging and underlies the age-related, neurodegenerative disorders Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). It will study the corollary hypotheses that a careful analysis of the pathobiology of superoxide dismutase (SOD1) mutations in familial ALS may provide insight into neuronal death in AD and PD and the SOD1 may be beneficial as a neuroprotectant. The Specific Aims are to: (1) Investigate patterns of oxidative injury in the central nervous system in situ in AD, PD and ALS, testing the hypotheses that tissues (Brain, plasma and urine) of patients with these diseases show increased oxidative damage compared to normal controls and that SOD1 inhibition or expression of mutant forms of SOD1 causes neuronal injury. (2) Investigate a model of chronic oxidative neurotoxicity in organotypic spinal cord cultures and use this model to analyze the role of antioxidants and neuroprotectants in preventing oxidative damage. The hypotheses are that chronic neurotoxicity in vitro can be produced by exposure to oxidants or inhibition of SOD1 and that this may be ameliorated with small molecule and protein antioxidants such as SOD1 or the proto-oncogene bcl-2. (3) Investigate a system for targeted, intraneuronal delivery of SOD1. This project will determine whether intraneuronal levels of SOD1 protein and enzyme activity may be enhanced through the use of a protein vector (the non-toxic, binding fragment of tetanus toxin) and whether this can modify patterns of oxidative injury in mammalian neurons. (4) Analyze the molecular pathology of mutations in SOD1 in yeast and study the role of SOD1 and other antioxidants in the aging process in yeast. This project will characterize the biochemical, physical and structural consequences of SOD1 mutations on SOD1 function. It will develop a yeast model to investigate oxidative injury in aging and how the aging process may be modified by manipulations of levels of SOD1 and other protein antioxidants. These projects will provide new information on oxidative pathology of aging in the brain; test the theory that accelerated free radical toxicity is a central feature of AD, PD and ALS; develop and employ simple eukaryotic models (yeast, neurons in vitro) as tools to investigate normal aging and cellular oxidant toxicity; and explore a novel fusion protein as a neuroprotectant antioxidant therapy in these and related diseases.